Sediment erosion and transport is critical to the ecological and commercial health of aquatic habitats from watershed to sea. There is now a consensus that microorganisms inhabiting the system mediate the erosive response of natural sediments ('ecosystem engineers') along with physicochemical properties. The biological mechanism is through secretion of a microbial organic glue (EPS: extracellular polymeric substances) that enhances binding forces between sediment grains to impact sediment stability and post-entrainment flocculation. The proposed work will elucidate the functional capability of heterotrophic bacteria, cyanobacteria and eukaryotic microalgae for mediating freshwater sediments to influence sediment erosion and transport. The potential and relevance of natural biofilms to provide this important 'ecosystem service' will be investigated for different niches in a freshwater habitat. Thereby, variations of the EPS 'quality' and 'quantity' to influence cohesion within sediments and flocs will be related to shifts in biofilm composition, sediment characteristics (e.g. organic background) and varying abiotic conditions (e.g. light, hydrodynamic regime) in the water body. Thus, the proposed interdisciplinary work will contribute to a conceptual understanding of microbial sediment engineering that represents an important ecosystem function in freshwater habitats. The research has wide implications for the water framework directive and sediment management strategies.
In the last decades agricultural policy has gained increasingly in complexity. Nowadays it influences the food and agricultural sector from the global market down to the farm level. Widespread research questions, like the impact of the WTO negotiations on the farm structure, most often require comprehensive modeling frameworks. Thus, different types of models are utilized according to their comparative advantages and combined in a strategically useful way to more accurately represent micro and macro aspects of the food and agricultural sector. Consequently, in recent years we have seen an increase in the development and application of model linkages. Given this background, the overall objective of this subproject is a systematic sensitivity analysis of model linkages that gradually involves more and more characteristics of the linkage and the corresponding transfer of results between models. In addition, the project aims to answer the following specific question: How does structural change at the farm level influence aggregate supply and technical progress? Under which conditions is it possible to derive macro-relationships from micro-relationships? How does the aggregation level influence the model results and how can possible problems be overcome? This procedure is used to quantify the effects and to derive conditions for optimal interaction of the connected models. The analysis is based on the general equilibrium model GTAP (Global Trade Analysis Project) and the farm group model FARMIS (Farm Modelling Information System) which are employed in conjunction to analyze the effects of WTO negotiations on the farm level.
Dissolved organic matter (DOM) is one major source of subsoil organic matter (OM). P5 aims at quantifying the impact of DOM input, transport, and transformation to the OC storage in the subsoil environment. The central hypotheses of this proposal are that in matric soil the increasing 14C age of organic carbon (OC) with soil depth is due to a cascade effect, thus, leading to old OC in young subsoil, whereas within preferential flowpaths sorptive stabilization is weak, and young and bioa-vailable DOM is translocated to the subsoil at high quantities. These hypotheses will be tested by a combination of DOC flux measurements with the comparative analysis of the composition and the turnover of DOM and mineral-associated OM. The work programme utilizes a DOM monitoring at the Grinderwald subsoil observatory, supplemented by defined experiments under field and labora-tory conditions, and laboratory DOM leaching experiments on soils of regional variability. A central aspect of the experiments is the link of a 13C-leaf litter labelling experiment to the 14C age of DOM and OM. With that P5 contributes to the grand goal of the research unit and addresses the general hypotheses that subsoil OM largely consists of displaced and old OM from overlying horizons, the sorption capacity of DOM and the pool size of mineral-associated OM are controlled by interaction with minerals, and that preferential flowpaths represent 'hot spots' of high substrate availability.
Dairy farming across Germany displays diverse production systems. Factor endowment, management, technology adoption as well as competitive dynamics in the local or regional land, agribusiness and dairy processing sectors contribute to this differentiation on farm level. These differences impact on the ability of dairy farms and regional dairy production systems to successfully respond to pressures arising from future market and policy changes. The overall objective of the research activities of which this project is a part of, is to develop a thorough understanding of the processes that govern the spatial dynamics of dairy farm development in different regions in Germany. The central hypothesis of this research project is that management system and technological choices differ systematically across local production and market conditions. The empirical approach will focus on the estimation of farm specific nonparametric cost functions for dairy farms located in across Germany differentiated by time and location. A spatially differentiated data base with information on input use, resource availability, as well as local market conditions for land and output markets will be compiled. The nonparametric approach is specifically suited to disclose a more accurate representation of dairy production system heterogeneity across locations and time compared to parametric concepts as it provides the necessary flexibility to accommodate non-linearities relevant for a wide domain of explanatory variables. The methodology employed goes beyond the state of the art of the literature as it combines kernel density estimation with a Bayesian sampling approach to provide theory consistent parameters for each farm in the data sample.The specific methodological hypothesis is that the nonparametric approach is superior to current parametric techniques and this hypothesis is tested using statistical model evaluation. Regarding the farm management and technological choices, we hypothesize that land suitability for feed production determines the farm intensity of dairy production and thus management and technological choices. With respect to the ability of farms to successfully respond to market pressures we hypothesize that farms at the upper and lower tail of the intensity distribution both can generate positive returns from dairy production. These last two hypotheses will be tested using the estimated spatially differentiated farm specific costs and marginal costs.The expected outcomes are of relevance for the agricultural sector and the food supply chain economy as a whole as fundamental market structure changes in the dairy sector are ongoing due to the abolition of the quota regulation in the years 2014/2015. Thus, exact knowledge about differences and development of dairy cost heterogeneity of farms within and between regions are an important factor for the actors involved in the market as well as the political support of this process.
In many plant species, FLOWERING LOCUS T and related proteins are the mobile signal that communicates information on photoperiod from the leaves to the shoots, where the transition to flowering is realized. FT expression is tightly controlled at the transcriptional level so that it is restricted to leaves, occurs only in appropriate photoperiods, and integrates ambient temperature and developmental cues, as well as information on biotic and abiotic stress. We previously established that FT transcription in the model plant Arabidopsis thaliana requires proximal promoter cis-elements and a distal enhancer, both evolutionary conserved among Brassicacea species. In addition, FT transcription is blocked prior vernalization in biannual accessions and vernalization-dependency of FT is controlled through a CArG-box located in the first intron that binds the transcriptional repressor FLOWERING LOCUS C (FLC). Chromatin-mediated repression by the Polycomb Group (PcG) pathway is required for photoperiod-dependent FT regulation and participates in FT expression level modulation in response to other cues.In this project, I propose to explore the available sequence data from the 1001 genome project in Arabidopsis to evaluate how often changes in regulatory cis-elements at FT have occurred and how these translate into an adaptive value. Allele-specific FT expression pattern will be measured in F1 hybrids of different accessions in response to varying environmental conditions. FT alleles that show cis-regulatory variation will be further analyzed to pinpoint the causal regulatory changes and study their effect in more detail. The allotetrapolyploid species Brassica napus is a hybrid of two Brassiceae species belonging to the A- and C-type genome, which are in turn mesopolyploid due to a genome triplication that occurred ca. 10x106 years ago. We will determine allele-specific expression of FT paralogs from both genomes of a collection of B. napus accessions. The plants will be grown in the field in changing environmental conditions to maximize the chance to detect expression variation of the paralogs. We will compare the contribution of the founder genomes to the regulation of flowering time and asses variation in this contribution. A particular focus will be to study the impact of chromatin-mediated repression on allele selection in B. napus.
Recent and predicted increases in extremely dry and hot summers emphasise the need for silvicultural approaches to increase the drought tolerance of existing forests in the short-term, before adaptation through species changes may be possible. We aim to investigate whether resistance during droughts, as well as the recovery following drought events (resilience), can be increased by allocating more growing space to individual trees through thinning. Thinning increases access of promoted trees to soil stored water, as long as this is available. However, these trees may also be disadvantaged through a higher transpirational surface, or the increased neighbourhood competition by ground vegetation. To assess whether trees with different growing space differ in drought tolerance, tree discs and cores from thinning experiments of Pinus sylvestris and Pseudotsuga menziesii stands will be used to examine transpirational stress and growth reduction during previous droughts as well as their subsequent recovery. Dendroecology and stable isotopes of carbon and oxygen in tree-rings will be used to quantify how assimilation rate and stomatal conductance were altered through thinning. The results will provide crucial information for the development of short-term silvicultural adaptation strategies to adapt forest ecosystems to climate change. In addition, this study will improve our understanding of the relationship between resistance and resilience of trees in relation to extreme stress events.
Water is an intrinsic component of ecosystems acting as a key agent of lateral transport for particulate and dissolved nutrients, forcing energy transfers, triggering erosion, and driving biodiversity patterns. Given the drastic impact of land use and climate change on any of these components and the vulnerability of Ecuadorian ecosystems with regard to this global change, indicators are required that not merely describe the structural condition of ecosystems, but rather capture the functional relations and processes. This project aims at investigating a set of such functional indicators from the fields of hydrology and biogeochemistry. In particular we will investigate (1) flow regime and timing, (2) nutrient cycling and flux rates, and (3) sediment fluxes as likely indicators. For assessing flow regime and timing we will concentrate on studying stable water isotopes to estimate mean transit time distributions that are likely to be impacted by changes in rainfall patterns and land use. Hysteresis loops of nitrate concentrations and calculated flux rates will be used as functional indicators for nutrient fluxes, most likely to be altered by changes in temperature as well as by land use and management. Finally, sediment fluxes will be measured to indicate surface runoff contribution to total discharge, mainly influenced by intensity of rainfall as well as land use. Monitoring of (1) will be based on intensive sampling campaigns of stable water isotopes in stream water and precipitation, while for (2) and (3) we plan to install automatic, high temporal-resolution field analytical instruments. Based on the data obtained by this intensive, bust cost effective monitoring, we will develop the functional indicators. This also provides a solid database for process-based model development. Models that are able to simulate these indicators are needed to enable projections into the future and to investigate the resilience of Ecuadorian landscape to global change. For the intended model set up we will couple the Catchment Modeling Framework, the biogeochemical LandscapeDNDC model and semi-empirical models for aquatic diversity. Global change scenarios will then be analyzed to capture the likely reaction of functional indicators. Finally, we will contribute to the written guidelines for developing a comprehensive monitoring program for biodiversity and ecosystem functions. Right from the beginning we will cooperate with four SENESCYT companion projects and three local non-university partners to ensure that the developed monitoring program will be appreciated by locals and stakeholders. Monitoring and modelling will focus on all three research areas in the Páramo (Cajas National Park), the dry forest (Reserva Laipuna) and the tropical montane cloud forest (Reserva Biologica San Francisco).
Subproject 3 will investigate the effect of shifting from continuously flooded rice cropping to crop rotation (including non-flooded systems) and diversified crops on the soil fauna communities and associated ecosystem functions. In both flooded and non-flooded systems, functional groups with a major impact on soil functions will be identified and their response to changing management regimes as well as their re-colonization capability after crop rotation will be quantified. Soil functions corresponding to specific functional groups, i.e. biogenic structural damage of the puddle layer, water loss and nutrient leaching, will be determined by correlating soil fauna data with soil service data of SP4, SP5 and SP7 and with data collected within this subproject (SP3). In addition to the field data acquired directly at the IRRI, microcosm experiments covering the broader range of environmental conditions expected under future climate conditions will be set up to determine the compositional and functional robustness of major components of the local soil fauna. Food webs will be modeled based on the soil animal data available to gain a thorough understanding of i) the factors shaping biological communities in rice cropping systems, and ii) C- and N-flow mediated by soil communities in rice fields. Advanced statistical modeling for quantification of species - environment relationships integrating all data subsets will specify the impact of crop diversification in rice agro-ecosystems on soil biota and on the related ecosystem services.
Organotin and especially butyltin compounds are used for a variety of applications, e.g. as biocides, stabilizers, catalysts and intermediates in chemical syntheses. Tributyltin (TBT) compounds exhibit the greatest toxicity of all organotins and have even been characterized as one of the most toxic groups of xenobiotics ever produced and deliberately introduced into the environment. TBT is not only used as an active biocidal compound in antifouling paints, which are designed to prevent marine and freshwater biota from settlement on ship hulls, harbour and offshore installations, but also as a biocide in wood preservatives, textiles, dispersion paints and agricultural pesticides. Additionally, it occurs as a by-product of mono- (MBT) and dibutyltin (DBT) compounds, which are used as UV stabilizer in many plastics and for other applications. Triphenyltin (TPT) compounds are also used as the active biocide in antifouling paints outside Europe and furthermore as an agricultural fungicide since the early 1960s to combat a range of fungal diseases in various crops, particularly potato blight, leaf spot and powdery mildew on sugar beet, peanuts and celery, other fungi on hop, brown rust on beans, grey moulds on onions, rice blast and coffee leaf rust. Although the use of TBT and TPT was regulated in many countries world-wide from restrictions for certain applications to a total ban, these compounds are still present in the environment. In the early 1970s the impact of TBT on nontarget organisms became apparent. Among the broad variety of malformations caused by TBT in aquatic animals, molluscs have been found to be an extremely sensitive group of invertebrates and no other pathological condition produced by TBT at relative low concentrations rivals that of the imposex phenomenon in prosobranch gastropods speaking in terms of sensitivity. TBT induces imposex in marine prosobranchs at concentrations as low as 0,5 ng TBT-Sn/L. Since 1993, for the littorinid snail Littorina littorea a second virilisation phenomenon, termed intersex, is known. In female specimens affected by intersex the pallial oviduct is transformed of towards a male morphology with a final supplanting of female organs by the corresponding male formations. Imposex and intersex are morphological alterations caused by a chronic exposure to ultra-trace concentrations of TBT. A biological effect monitoring offers the possibility to determine the degree of contamination with organotin compounds in the aquatic environment and especially in coastal waters without using any expensive analytical methods. Furthermore, the biological effect monitoring allows an assessment of the existing TBT pollution on the basis of biological effects. Such results are normally more relevant for the ecosystem than pure analytical data. usw.
It has been suggested that dying and decaying fine roots and root exudation represent important, if not the most important, sources of soil organic carbon (SOC) in forest soils. This may be especially true for deep-reaching roots in the subsoil, but precise data to prove this assumption are lacking. This subproject (1) examines the distribution and abundance of fine roots (greater than 2 mm diameter) and coarse roots (greater than 2 mm) in the subsoil to 240 cm depth of the three subsoil observatories in a mature European beech (Fagus sylvatica) stand, (2) quantifies the turnover of beech fine roots by direct observation (mini-rhizotron approach), (3) measures the decomposition of dead fine root mass in different soil depths, and (4) quantifies root exudation and the N-uptake potential with novel techniques under in situ conditions with the aim (i) to quantify the C flux to the SOC pool upon root death in the subsoil, (ii) to obtain a quantitative estimate of root exudation in the subsoil, and (iii) to assess the uptake activity of fine roots in the subsoil as compared to roots in the topsoil. Key methods applied are (a) the microscopic distinction between live and dead fine root mass, (b) the estimation of fine and coarse root age by the 14C bomb approach and annual ring counting in roots, (c) the direct observation of the formation and disappearance of fine roots in rhizotron tubes by sequential root imaging (CI-600 system, CID) and the calculation of root turnover, (d) the measurement of root litter decomposition using litter bags under field and controlled laboratory conditions, (e) the estimation of root N-uptake capacity by exposing intact fine roots to 15NH4+ and 15NO3- solutions, and (f) the measurement of root exudation by exposing intact fine root branches to trap solutions in cuvettes in the field and analysing for carbohydrates and amino acids by HPLC and Py-FIMS (cooperation with Prof. A. Fischer, University of Trier). The obtained data will be analysed for differences in root abundance and activity between subsoil (100-200 cm) and topsoil (0-20 cm) and will be related to soil chemical and soil biological data collected by the partner projects that may control root turnover and exudation in the subsoil. In a supplementary study, fine root biomass distribution and root turnover will also be studied at the four additional beech sites for examining root-borne C fluxes in the subsoil of beech forests under contrasting soil conditions of different geological substrates (Triassic limestone and sandstone, Quaternary sand and loess deposits).
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